2002 JEEP GRAND CHEROKEE control brake module

CONDITION POSSIBLE CAUSES CORRECTION
FOG LAMPS DO NOT
ILLUMINATE1. Blown fuse for fog lamp. 1. Replace fuse. Refer to Electrical, Wiring
Information.
2. No Z1-ground at fog lamps. 2. Repair circuit ground. Refer to Electrical,
Wiring Information.
3. Faulty multifunction switch. 3. Refer to Electrical, Wiring Information.
4. Broken connector terminal or wire
splice in fog lamp circuit.4. Repair connector terminal or wire splice.
5. Defective or burned out bulb. 5. Replace bulb.
DAYTIME RUNNING LAMP
CONDITION POSSIBLE CAUSES CORRECTION
DAYTIME RUNNING LAMPS DO
NOT WORK1. Poor connection at DRL module. 1. Secure connector on DRL
module.
2. Parking brake engaged. 2. Disengage parking brake.
3. Parking brake circuit shorted to
ground.3. Check cluster telltale, refer to
Group 8W.
4. Headlamp circuit shorted to
ground.4. Refer to Group 8W.
5. Defective DRL relay. 5. Replace DRL relay.
6. Body controller not programed
with Canadian country code.6. Check country code.
7. DRL relay is missing. 7. Install DRL relay.
8. Blown fuse for DRL. 8. Replace fuse refer to Electrical,
Wiring Information.
Clicking or chattering when DRL is
on.1. Mechanical relay is installed in
the junction block.1. Ensure that the DRL relay is
installed in the proper socket in
junction block, and that no
mechanical relay exists in the low
beam socket.
DIAGNOSIS AND TESTING Ð HEADLAMP
WARNING: EYE PROTECTION SHOULD BE USED
WHEN SERVICING GLASS COMPONENTS. PER-
SONAL INJURY CAN RESULT.
CAUTION: Do not touch the glass of halogen bulbs
with fingers or other possibly oily surface, reduced
bulb life will result. Do not use bulbs other than
those indicated in the Bulb Application table. Dam-
age to lamp and/or Daytime Running Lamp Module
can result. Do not use fuses, circuit breakers or
relays having greater amperage value than indi-
cated on the fuse panel or in the Owners Manual.
Each vehicle is equipped with various lamp assem-
blies. A good power feed and ground are necessary forproper lighting operation. Grounding is provided by
the lamp socket when it comes in contact with the
metal body, or through a separate ground wire.
When changing lamp bulbs check the socket for
corrosion. If corrosion is present, clean it with a wire
brush and coat the inside of the socket lightly with
Mopar Multi-Purpose Grease or equivalent.
REMOVAL - BULB
(1) Remove the headlamp.
(2) Turn the bulb socket one quarter turn counter
clockwise.
(3) Remove the socket from lamp (Fig. 13).
(4) Remove the bulb from socket.
8L - 14 LAMPS/LIGHTING - EXTERIORWJ
HEADLAMP (Continued)

MULTI-FUNCTION SWITCH - INSTALLATION -
LEFT MULTI-FUNCTION SWITCH).
(6) Reinstall the clockspring onto the multi-func-
tion switch housing. (Refer to 8 - ELECTRICAL/RE-
STRAINTS/CLOCKSPRING - INSTALLATION).
(7) Reconnect the battery negative cable.
PARK/TURN SIGNAL LAMP
REMOVAL - BULBS
(1) Remove the headlamp module.
(2) Rotate the turn signal bulb socket 1/4 turn
counter clockwise.
(3) Remove the bulb socket from module.
(4) Remove the bulb from socket.
INSTALLATION - BULBS
(1) Press the bulb into socket.
(2) Position the bulb socket in module.
(3) Rotate the turn signal bulb socket 1/4 turn
clockwise.
(4) Install the headlamp module.
TAIL LAMP
DESCRIPTION
The taillamp module contains a housing, lens, and
three bulbs. A dual filament bulb is used for tail and
stop functions. A single filament bulb is used for turn
signal operations. A separate bulb is used for back-up
illumination.
OPERATION
All exterior lighting function are controlled by the
multifunction switch. Stop lamp functions are con-
trolled by the stoplamp switch. The back-up lamps
are controlled by the back-up lamp switch.
REMOVAL
REMOVAL - BULBS
The brake, turn signal, back-up, and side marker
lamp bulbs are incorporated into the tail lamp.
(1) Remove the tail lamp.
(2) Rotate the bulb socket counterclockwise.
(3) Separate the socket from the lamp
(4) Remove the bulb from the socket (Fig. 32).
REMOVAL - LAMP
The brake, turn signal, back-up, and side marker
lamps are incorporated in the tail lamp.
(1) Remove the screws attaching the lamp to body
(Fig. 33).
(2) Disengage the lamp from the alignment pin.
(3) Disconnect lamp wire harness connector.
(4) Separate lamp from vehicle.
Fig. 31 Multi-Function Switch Mounting Housing
Screw Remove/Install
1 - CLOCK SPRING
2 - SCREW
3 - MULTI-FUNCTION SWITCH MOUNTING HOUSING
Fig. 32 Tail Lamp Bulbs
1 - TAIL/STOP BULB
2 - TAIL LAMP
3 - BACK-UP BULB
4 - TURN SIGNAL BULB
WJLAMPS/LIGHTING - EXTERIOR 8L - 25
LEFT MULTI-FUNCTION SWITCH (Continued)

ACTIVE RESTRAINTS
The active restraints for this model include:
²Front Seat Belts- Both front seating positions
are equipped with three-point seat belt systems
employing a lower B-pillar mounted inertia latch-
type retractor, height-adjustable upper B-pillar
mounted turning loops, a fixed lower seat belt anchor
secured to the lower B-pillar, and a fixed end-release
seat belt buckle secured to the side of the floor panel
transmission tunnel. Both front seat belt buckles
include an integral Hall-effect seat belt switch that
detects whether its respective seat belt has been fas-
tened.
²Rear Seat Belts- Both outboard rear seating
positions are equipped with three-point seat belt sys-
tems. The outboard seating position belts employ a
lower C-pillar mounted inertia latch-type retractor,
height-adjustable upper C-pillar mounted turning
loops, and a fixed lower seat belt anchor secured to
the floor panel. The center rear seating position of
vehicles manufactured for sale in North America has
a lap belt that is anchored to the rear floor panel
with the right outboard seat belt buckle. Vehicles
manufactured for sale outside of North America are
equipped with a three-point seat belt in the rear seat
center seating position. This seat belt has an inertia
latch-type retractor that is integral to the rear seat
back panel, and the lower belt anchor is secured to
the rear floor panel with the right outboard seat belt
buckle. A cable from the seat back latch locks the
center belt retractor spool unless the seat back is
fully latched. All three rear seat belts have fixed end-
release seat belt buckles secured to the rear floor
panel, a single buckle unit on the right side and a
double buckle unit on the left side.
²Child Seat Tether Anchors- All vehicles are
equipped with three, fixed-position, child seat upper
tether anchors and two lower anchors. Two upper
anchors are integral to the back of the right rear seat
back panel, and one is integral to the left rear seat
back panel. The two lower anchors are integral to the
outboard rear seat back brackets.
PASSIVE RESTRAINTS
The passive restraints available for this model
include the following:
²Dual Front Airbags- Multistage driver and
front passenger airbags are available for this model.
This airbag system is a passive, inflatable, Supple-
mental Restraint System (SRS) and vehicles with
this equipment can be readily identified by the ªSRS
- AIRBAGº logo molded into the driver airbag trim
cover in the center of the steering wheel and also
into the passenger airbag door area of the instru-
ment panel top pad above the glove box (Fig. 2).
Vehicles with the airbag system can also be identifiedby the airbag indicator, which will illuminate in the
instrument cluster for about seven seconds as a bulb
test each time the ignition switch is turned to the On
position.
²Side Curtain Airbags- Optional side curtain
airbags are available for this model when it is also
equipped with dual front airbags. This airbag system
is a passive, inflatable, Supplemental Restraint Sys-
tem (SRS) and vehicles with this equipment can be
readily identified by a molded identification trim but-
ton with the ªSRS - AIRBAGº logo located on the
headliner above each B-pillar (Fig. 2).
The supplemental restraint system includes the
following major components, which are described in
further detail elsewhere in this service information:
²Airbag Control Module- The Airbag Control
Module (ACM) is also sometimes referred to as the
Occupant Restraint Controller (ORC). The ACM is
located on a mount on the floor panel transmission
tunnel near the park brake release mechanism,
under the center floor console.
²Airbag Indicator- The airbag indicator is inte-
gral to the ElectroMechanical Instrument Cluster
(EMIC), which is located on the instrument panel in
front of the driver.
²Clockspring- The clockspring is located near
the top of the steering column, directly beneath the
steering wheel.
²Driver Airbag- The driver airbag is located in
the center of the steering wheel, beneath the driver
airbag trim cover.
²Driver Knee Blocker- The driver knee blocker
is a structural unit secured to the back side of and
integral to the instrument panel steering column
opening cover.
²Front Impact Sensor- Two front impact sen-
sors are used on vehicles equipped with dual front
airbags, one left side and one right side. One sensor
is located on a bracket on the lower inboard side of
each vertical member of the radiator support.
Fig. 2 SRS Logo
WJRESTRAINTS 8O - 3
RESTRAINTS (Continued)

(4) Check to be certain that nobody is in the vehi-
cle, then reconnect the battery negative cable.
(5) Using the DRBIIIt, read and record the active
(current) Diagnostic Trouble Code (DTC) data.
(6) Next, use the DRBIIItto read and record any
stored (historical) DTC data.
(7) If any DTC is found in Step 5 or Step 6, refer
to the appropriate diagnostic information.
(8) Use the DRBIIItto erase the stored DTC data.
If any problems remain, the stored DTC data will not
erase. Refer to the appropriate diagnostic informa-
tion to diagnose any stored DTC that will not erase.
If the stored DTC information is successfully erased,
go to Step 9.
(9) Turn the ignition switch to the Off position for
about fifteen seconds, and then back to the On posi-
tion. Observe the airbag indicator in the instrument
cluster. It should light for six to eight seconds, and
then go out. This indicates that the supplemental
restraint system is functioning normally and that the
repairs are complete. If the airbag indicator fails to
light, or lights and stays on, there is still an active
supplemental restraint system fault or malfunction.
Refer to the appropriate diagnostic information to
diagnose the problem.
AIRBAG CONTROL MODULE
DESCRIPTION
The Airbag Control Module (ACM) is also some-
times referred to as the Occupant Restraint Control-
ler (ORC) (Fig. 6). The ACM is concealed underneath
the center floor console, where it is secured by four
screws to a stamped steel mounting bracket welded
onto the top of the floor panel transmission tunnel
just forward of the park brake mechanism in the pas-
senger compartment of the vehicle.
Concealed within a hollow in the center of the die
cast aluminum ACM housing is the electronic cir-
cuitry of the ACM which includes a microprocessor,
an electronic impact sensor, an electronic safing sen-
sor, and an energy storage capacitor. A stamped
metal cover plate is secured to the bottom of the
ACM housing with four screws to enclose and protect
the internal electronic circuitry and components. A
printed label on the top of the ACM housing provides
a visual verification of the proper orientation of the
unit, and should always be pointed toward the front
of the vehicle.
Two molded plastic electrical connector receptacles
exit the forward side of the ACM housing. These two
receptacles connect the ACM to the vehicle electrical
system through a dedicated take out and connector of
the instrument panel wire harness, and a dedicated
take out and connector of the airbag overlay wire
harness. For vehicles equipped with the optional side
curtain airbags, both ACM connector receptacles are
black in color and the ACM contains a second bi-di-
rectional safing sensor for the side airbags. For vehi-
cles not equipped with the optional side curtain
airbags, the ACM connector receptacles are both
gray.
The impact sensor and safing sensor internal to
the ACM are calibrated for the specific vehicle, and
are only serviced as a unit with the ACM. The ACM
cannot be repaired or adjusted and, if damaged or
faulty, it must be replaced.
OPERATION
The microprocessor in the Airbag Control Module
(ACM) contains the supplemental restraint system
logic circuits and controls all of the supplemental
restraint system components. The ACM uses
On-Board Diagnostics (OBD) and can communicate
with other electronic modules in the vehicle as well
as with the DRBIIItscan tool using the Programma-
ble Communications Interface (PCI) data bus net-
work. This method of communication is used for
control of the airbag indicator in the ElectroMechani-
cal Instrument Cluster (EMIC) and for supplemental
restraint system diagnosis and testing through the
16-way data link connector located on the driver side
lower edge of the instrument panel. (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/COMMUNICATION - OPERATION).
Fig. 6 Airbag Control Module
1 - AIRBAG CONTROL MODULE
2 - ORIENTATION ARROW
3 - LABEL
4 - MOUNTING HOLES (4)
5 - CONNECTOR RECEPTACLE (2)
WJRESTRAINTS 8O - 9
RESTRAINTS (Continued)

WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, FRONT IMPACT SENSOR,
SIDE IMPACT SENSOR, SIDE CURTAIN AIRBAG, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. DISCONNECT AND ISOLATE THE BAT-
TERY NEGATIVE (GROUND) CABLE, THEN WAIT
TWO MINUTES FOR THE SYSTEM CAPACITOR TO
DISCHARGE BEFORE PERFORMING FURTHER
DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE
WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
WARNING: THE AIRBAG CONTROL MODULE CON-
TAINS THE IMPACT SENSOR, WHICH ENABLES
THE SYSTEM TO DEPLOY THE SUPPLEMENTAL
RESTRAINTS. NEVER STRIKE OR DROP THE AIR-
BAG CONTROL MODULE, AS IT CAN DAMAGE THE
IMPACT SENSOR OR AFFECT ITS CALIBRATION. IF
AN AIRBAG CONTROL MODULE IS ACCIDENTALLY
DROPPED DURING SERVICE, THE MODULE MUST
BE SCRAPPED AND REPLACED WITH A NEW UNIT.
FAILURE TO OBSERVE THIS WARNING COULD
RESULT IN ACCIDENTAL, INCOMPLETE, OR
IMPROPER SUPPLEMENTAL RESTRAINT DEPLOY-
MENT AND POSSIBLE OCCUPANT INJURIES.
(1) Disconnect and isolate the battery negative
cable. Wait two minutes for the system capacitor to
discharge before further service.
(2) Remove the center console from the top of the
floor panel transmission tunnel. (Refer to 23 - BODY/
INTERIOR/FLOOR CONSOLE - REMOVAL).
(3) Remove the two nuts that secure the center
console bracket to the studs on the floor panel trans-
mission tunnel just forward of the Airbag Control
Module (ACM) (Fig. 7).
(4) Remove the center console bracket from the
two studs on the floor panel transmission tunnel.
(5) Disconnect the airbag overlay wire harness
connector for the ACM from the ACM connector
receptacle (Fig. 8). To disconnect the airbag overlay
wire harness connector from the ACM:
(a) Slide the red Connector Position Assurance
(CPA) lock on the top of the connector toward the
front of the vehicle.
(b) Depress the forward edge of the CPA lock to
release the connector latch tab and pull the connec-
tor straight away from the ACM connector recepta-
cle.(6) Disconnect the instrument panel wire harness
connector for the ACM from the ACM connector
receptacle.
Fig. 7 Center Console Bracket Remove/Install
1 - SHIFTER
2 - NUT (2)
3 - BRACKET
4 - PARK BRAKE LEVER
5 - AIRBAG CONTROL MODULE
6 - FLOOR PANEL TRANSMISSION TUNNEL
7 - INSTRUMENT PANEL WIRE HARNESS
Fig. 8 Airbag Control Module Connector
1 - INSTRUMENT PANEL WIRE HARNESS CONNECTOR
2 - LATCH TAB
3 - CPA LOCK
4 - AIRBAG OVERLAY WIRE HARNESS CONNECTOR
5 - AIRBAG CONTROL MODULE
WJRESTRAINTS 8O - 11
AIRBAG CONTROL MODULE (Continued)

SPEED CONTROL
TABLE OF CONTENTS
page page
SPEED CONTROL
DESCRIPTION..........................1
OPERATION............................1
DIAGNOSIS AND TESTING - ROAD TEST.....2
SPECIFICATIONS
TORQUE - SPEED CONTROL.............3
CABLE
DESCRIPTION..........................3
OPERATION............................3
REMOVAL
REMOVAL - 4.0L.......................3
REMOVAL - 4.7L.......................3
INSTALLATION
INSTALLATION - 4.0L...................4
INSTALLATION - 4.7L...................4
SERVO
DESCRIPTION..........................5OPERATION............................5
REMOVAL.............................5
INSTALLATION..........................6
SWITCH
DESCRIPTION..........................7
OPERATION............................7
REMOVAL.............................7
INSTALLATION..........................7
VACUUM RESERVOIR
DESCRIPTION..........................8
OPERATION............................8
DIAGNOSIS AND TESTING - VACUUM
RESERVOIR..........................8
REMOVAL.............................8
INSTALLATION..........................9
SPEED CONTROL
DESCRIPTION
The speed control system is electronically con-
trolled and vacuum operated. Electronic control of
the speed control system is integrated into the Pow-
ertrain Control Module (PCM). The controls consist
of two steering wheel mounted switches. The
switches are labeled: ON/OFF, RES/ACCEL, SET,
COAST, and CANCEL.
The system is designed to operate at speeds above
30 mph (50 km/h).
WARNING: THE USE OF SPEED CONTROL IS NOT
RECOMMENDED WHEN DRIVING CONDITIONS DO
NOT PERMIT MAINTAINING A CONSTANT SPEED,
SUCH AS IN HEAVY TRAFFIC OR ON ROADS THAT
ARE WINDING, ICY, SNOW COVERED, OR SLIP-
PERY.
OPERATION
When speed control is selected by depressing the
ON switch, the PCM allows a set speed to be stored
in PCM RAM for speed control. To store a set speed,
depress the SET switch while the vehicle is moving
at a speed between 35 and 85 mph. In order for the
speed control to engage, the brakes cannot be
applied, nor can the gear selector be indicating the
transmission is in Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
²Depressing the clutch pedal (if equipped).
NOTE: Depressing the OFF switch or turning off the
ignition switch will erase the set speed stored in
the PCM.
For added safety, the speed control system is pro-
grammed to disengage for any of the following condi-
tions:
²An indication of Park or Neutral
²A rapid increase rpm (indicates that the clutch
has been disengaged)
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The speed signal increases at a rate of 10 mph
per second (indicates that the coefficient of friction
between the road surface and tires is extremely low)
WJSPEED CONTROL 8P - 1

(8) Connect negative battery cable at battery.
(9) Before starting engine, operate accelerator
pedal to check for any binding.
SERVO
DESCRIPTION
The servo unit consists of a solenoid valve body,
and a vacuum chamber. The solenoid valve body con-
tains three solenoids:
²Vacuum
²Vent
²Dump
The vacuum chamber contains a diaphragm with a
cable attached to control the throttle linkage.
OPERATION
The Powertrain Control Module (PCM) controls the
solenoid valve body. The solenoid valve body controls
the application and release of vacuum to the dia-
phragm of the vacuum servo. The servo unit cannot
be repaired and is serviced only as a complete assem-
bly.
Power is supplied to the servo's by the PCM
through the brake switch. The PCM controls the
ground path for the vacuum and vent solenoids.The dump solenoid is energized anytime it receives
power. If power to the dump solenoid is interrupted,
the solenoid dumps vacuum in the servo. This pro-
vides a safety backup to the vent and vacuum sole-
noids.
The vacuum and vent solenoids must be grounded
at the PCM to operate. When the PCM grounds the
vacuum servo solenoid, the solenoid allows vacuum
to enter the servo and pull open the throttle plate
using the cable. When the PCM breaks the ground,
the solenoid closes and no more vacuum is allowed to
enter the servo. The PCM also operates the vent sole-
noid via ground. The vent solenoid opens and closes a
passage to bleed or hold vacuum in the servo as
required.
The PCM duty cycles the vacuum and vent sole-
noids to maintain the set speed, or to accelerate and
decelerate the vehicle. To increase throttle opening,
the PCM grounds the vacuum and vent solenoids. To
decrease throttle opening, the PCM removes the
grounds from the vacuum and vent solenoids. When
the brake is released, if vehicle speed exceeds 30
mph to resume, 35 mph to set, and the RES/ACCEL
switch has been depressed, ground for the vent and
vacuum circuits is restored.
REMOVAL
The speed control servo is attached to a bracket.
The bracket and servo assembly are located below
the battery tray.
(1) Disconnect negative battery cable at battery.
(2) Disconnect positive battery cable at battery.
(3) Remove air cleaner housing at top of throttle
body and disconnect servo cable at throttle body.
Refer to Servo Cable Removal/Installation.
(4) Remove battery from battery tray.
(5) Disconnect wiring at battery tray.
(6) Disconnect positive battery cable at Power Dis-
tribution Center (PDC).
(7) Loosen PDC at battery tray.
(8) Remove 4 battery tray bolts. One of these bolts
attaches to speed control bracket flange that sup-
ports battery tray. While removing battery tray, dis-
connect battery temperature sensor electrical
connector at sensor.
(9) Disconnect vacuum line at servo vacuum hose
fitting (Fig. 5) .
(10) Disconnect electrical connector at servo (Fig.
5) .
If servo and mounting bracket are being removed
as one assembly, remove two mounting nuts (Fig. 5) .
These are located above right-front tire. Remove
inner fender clips and pry inner fender back slightly
to gain access to mounting nuts.
Fig. 4 Speed Control Cable at BracketÐ4.7L V-8
Engine
1 - PLASTIC CABLE MOUNT
2 - SPEED CONTROL CABLE
3 - BRACKET
4 - SLIDE FOR REMOVAL
WJSPEED CONTROL 8P - 5
CABLE (Continued)

SWITCH
DESCRIPTION
There are two separate switch pods that operate
the speed control system. The steering-wheel-
mounted switches use multiplexed circuits to provide
inputs to the PCM for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
OPERATION
When speed control is selected by depressing the
ON, OFF switch, the PCM allows a set speed to be
stored in its RAM for speed control. To store a set
speed, depress the SET switch while the vehicle is
moving at a speed between approximately 35 and 85
mph. In order for the speed control to engage, the
brakes cannot be applied, nor can the gear selector
be indicating the transmission is in Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
The speed control can be disengaged also by any of
the following conditions:
²An indication of Park or Neutral
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²Depressing the clutch pedal.
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch restores the vehicle to
the target speed that was stored in the PCM's RAM.
NOTE: Depressing the OFF switch will erase the set
speed stored in the PCM's RAM.
If, while the speed control is engaged, the driver
wishes to increase vehicle speed, the PCM is pro-
grammed for an acceleration feature. With the
ACCEL switch held closed, the vehicle accelerates
slowly to the desired speed. The new target speed is
stored in the PCM's RAM when the ACCEL switch isreleased. The PCM also has a9tap-up9feature in
which vehicle speed increases at a rate of approxi-
mately 2 mph for each momentary switch activation
of the ACCEL switch.
The PCM also provides a means to decelerate with-
out disengaging speed control. To decelerate from an
existing recorded target speed, depress and hold the
COAST switch until the desired speed is reached.
Then release the switch. The ON, OFF switch oper-
ates two components: the PCM's ON, OFF input, and
the battery voltage to the brake switch, which powers
the speed control servo.
Multiplexing
The PCM sends out 5 volts through a fixed resistor
and monitors the voltage change between the fixed
resistor and the switches. If none of the switches are
depressed, the PCM will measure 5 volts at the sen-
sor point (open circuit). If a switch with no resistor is
closed, the PCM will measure 0 volts (grounded cir-
cuit). Now, if a resistor is added to a switch, then the
PCM will measure some voltage proportional to the
size of the resistor. By adding a different resistor to
each switch, the PCM will see a different voltage
depending on which switch is pushed.
Another resistor has been added to the 'at rest cir-
cuit' causing the PCM to never see 5 volts. This was
done for diagnostic purposes. If the switch circuit
should open (bad connection), then the PCM will see
the 5 volts and know the circuit is bad. The PCM will
then set an open circuit fault.
REMOVAL
WARNING: BEFORE BEGINNING ANY AIRBAG SYS-
TEM COMPONENT REMOVAL OR INSTALLATION,
REMOVE AND ISOLATE THE NEGATIVE (-) CABLE
FROM THE BATTERY. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. THEN
WAIT TWO MINUTES FOR SYSTEM CAPACITOR TO
DISCHARGE BEFORE FURTHER SYSTEM SERVICE.
FAILURE TO DO THIS COULD RESULT IN ACCIDEN-
TAL AIRBAG DEPLOYMENT AND POSSIBLE
INJURY.
(1) Disconnect and isolate negative battery cable.
(2) Remove airbag module. Refer to Group 8M,
Passive Restraint Systems.
(3) Remove electrical connector at switch.
(4) Remove switch-to-steering wheel mounting
screw (Fig. 7) .
(5) Remove switch.
INSTALLATION
(1) Install switch and mounting screw.
(2) Tighten screw to 1.5 N´m (15 in. lbs.) torque.
(3) Install electrical connector to switch.
WJSPEED CONTROL 8P - 7